As an example of a container to contain cosmetics such as face lotion, shampoo, rinse, liquid soap, food seasoning, or the like, a double-walled container (which is also called delamination container) is known. Such double-walled container includes the outer layer body that constitutes the outer shell of the container and the inner layer body that is accommodated inside the outer layer body and that is deformable to undergo volume reduction. Furthermore, the outer layer body is provided with an ambient air introduction hole that communicates between the outer layer body and the inner layer body, and only the inner layer body undergoes volume reduction in response to dispensing of the content medium.
The content medium may be dispensed by various methods, such as using a pump fitted to a mouth of the outer layer body, mainly utilizing squeezing of a trunk of the outer layer body, and mainly utilizing the own weight of the content medium (refer, for example, to Patent Literature 1). In a container using the pump, the configuration is complicated, and moreover, cost increase is inevitable. In a container utilizing squeezing of the outer layer body, the configuration is relatively simplified. However, to cause only the inner layer body to undergo volume reduction, it is necessary to provide an ambient air introduction valve that is configured to close the ambient air introduction hole when the outer layer body is pressed and to open the ambient air introduction hole when the pressure is released. On the other hand, a container utilizing the own weight of the content medium has a simplified configuration and besides, it does not need the ambient air introduction valve. Accordingly, such a container is excellent in cost reduction.
In particular, when such a container utilizing the own weight of the content medium is formed by blow molding a parison, a pinched-off portion formed due to pinch-off using a splittable mold in the blow molding may be used directly as the ambient air introduction hole. The parison has been formed by laminating the outer layer body made of a synthetic resin and the inner layer body made of another synthetic resin having low compatibility with the outer layer body. That is to say, by splitting a bottom wall of the outer layer body at the pinched-off portion, the inner layer body is separated from the inner layer body. Thus, the slit-shaped ambient air introduction hole is provided in the pinched-off portion.